Transmission system



Oct. 16, 1928. 1,687,883

- H. w. O'NEILL TRANSMISSION SYSTEM dP Q Oct. 16,1928.

H. W. ONEILL TRANSMISSION SYSTEM Filed Oct. 19, 1926 4 Sheets-Sheet 4 Patented Oct. 16, 1928.

UNITED STATES PATENT oF'FIcE..

HENRY w. nnILL, or nmvmcns'r, new iron-x," Assmrron To BELL .rnrnrnonn LABORATORIES, INCORPORATED, or NEW YORK, N. Y., A. conrom'rron' or nnw YORK.

TRANSMISSION SYSTEM,

Application filed October 19, 1.1926; Serialflo. 242,587.

This invention relates to transmission systems, and more particularly, to means and systems for joining land lines toradio channels.

The principal object of this invention is to provide an improved system for handling sound transmission overa chain of transmissionchannel's. v

In carrying out the present invention, facilities have been provided for affording socalled duplex service as regards the oppositely directioned transmissions of a telephone conversation. For this duplex arrangement, switching equipments at a first point, preferabl-ya telephone switching center at which toll and long distance land line telephone circuits may be connectivelyaccessible, are provided with transmission circuits and circuits. ancillary thereto which nlay be branched to a second switching point at which radio. transmitting equipment may 7 be present and also to athird switching point which may serve radio receiving equipments. Separation of the two latter points is desirable in situations particularly to be met by the present system where the radio sections may be characterized by considerablelen th or reat distances as. in transatlantic:-

telephone working.

Certain features of this invention. concern: the provlsion of facilities at the first switching point which may be indicated as a toll center, for branching a connection frorn'socalled two-wire linecircuits into afour-wire circuit formed of the transmission circuits the ancillary tion between the three points or, stations, may

also function as a monitoring circuit over; it which, an. attendant or operator may llsten in on a conversation over the transmission,

circuit. r v

An additional .teatureresldes in the provision of means whereby voice currents from a connection may reach the order-wire circuit while voice or signaling currents originating on the ordenwire hne,may not reach nor a'ifect the transmission circults of a connection.

This may be referred toas an; order-wire llIlEs'WlllCll 1n additlon to: serv ing as a means of slgnalmg and commumca-- A further feature resides in the provision of a duplicate switching equipment at the radio transmitting and the'radioreceiving;

' stations whereby a plurality of connections between the diflerent points may be set up over which an. attendant at either point may nate a'call and converse on a full duplex basis either over the radio portion or over the land lineportion of thefsystem.

Another feature relates to link circuits with associated-facilities, so arranged that the same links maybe employed either for two-wire or for four-wire working inconnec' tion with the workof handling calls and in completing connections; 7

Another feature provides means wherebyconnections maybe transferred for the purpose of quickly isolating portions of the switching equipments in which irregularities may'have developed, in substituting therefor duplicate equipments so that in meeting emergenciesz'of this nature service may-be. resumed or may continue without appreciable interruption or delay. V p

A still further feature relates to the pro vision of testing equipment associated with the switching systems in such a manner thatequipment or circuit irregularities either on the wire side, the radio side,'0r failures in the .linkcircuit equipments may besearchecl out and localized pa h- This invention is illustrated intheaecompanyingdrawings in which- Fig. 51 is in the form of a diagrammatic with certainty and plan which shows the general relation of. the

three switching points and the circuits by which they are: oined. one point with the others; v. I Fig. 2 shows at A, the circuit arrangement of the equipment at the first point or toll switching center with circuits extending to the radio transmitting, point B*and also circuits 7 extending point C; v I

Fig. 3 shows link and test circuit equipments at the radio transmitting point;

Fig. 4 shows circuits which serve: the radio transmitter proper and also certain portions of the switching equipment including the cirto the radio receiving cuits of an attendant or operators telephone set; i

Fig. 5 shows a circuit unit having an unidirectional conductive characteristic for use in supervising the conversation of a connection;

Fig. 6 shows a meter system for measuring the volume of transmission currents, while; Fig. 7 showsthe relation in which the sheets Figs. 2, 3 and 4 should be placed for convenience in tracing the circuits and the relation of the connections which may be made.

In describing this system attention will first be directed to Fig.1 of the drawing. At a telephone switching center, A,'two twowire circuits 1 and 2 having balancing net-- works 3 and 4, terminate respectlvely 1n 1acks 5 and 6, from which connections may be extended by means of a link circuit 7. The latter circuit is provided with keys at point 8,

an operators telephone set at 9, while at 10, a coil system also in association with the networks 3'and 4, is provided for converting the two-wire circuit of the linkinto a four-wire circuit. 01 this four-wire circuit one pair of conductors extend through a repeater 11 and leads 12 to a jack at the switching point B, while the other pair is routed by Way of arepeater 13 and leads 14 to a jack 120 at switching point C.

- "A circuit ancillary to the transmission cirjacks 20, 21, 24 and jacks 25, 26, 27 andv 28.

The latter acks serve equipment 29 of a radio transmitting system 30 which is provided with an antenna 31. At 32, there is provided equipment which may be employed for signaling or communicating by telegraph over i the radio transmitter, when desired.

A test cord. 33 isprovided witha jack 34 for the connection or meter equipment 35,

t and maybe employed for testing the circuits 7 jacks at this point. I serve as patching units in joining the test and apparatus connected with the various Jacks 36 and 37 may cord with either of the link or cord circuits 22 and 23, for testing such circuits.

Switching keys at 38 serve for converting the cord circuits 22 and 23 for either'twowire or ior four-wire working, and also serve for isolating the common equipment which includes an operators telephone set at 39, from either one of the cord equipments 22 or 23 on which irregularities may have developed, as already mentioned.

At 40 a coil system witha net work 41 provides that when a two-wire line as a line which may be assumed as'terminating in the jack 24, may be joined by means 01 a sooalled patching cord 45 with a jack 43, the two-Wire circuit will be converted into a four-wire circuit which may be connected from jacks 42 and 44 over the radio equipments as presently will be described.

At the station C, the reference characters 120to 144, inclusive, indicate equipmentsand devices corresponding respectively with those indicated at the station B by the reference characters 20' to 44 inclusive. C, however, the equipments 132, 130 and 131 are for radio reception rather than radio transmitting.

Under a wire-radio connection, link or cord 7 may be connected to jack 5, cord 22 connected to join jacks 20 and 25, while cord 122 may connect the jacks 120 and 125. At a distant point, equipments in duplicate of that shown in the drawing may be considered as present in similarly joining a land line to the distant equipment of the present radio channels in completing a connection. Therefore, incoming transmission from the line 1 may traverse the circuit portions 5, 7, 8, 10,11, 12,20, 22,

25,29 and 30 to be radiatedirom the transmitting antenna 31, while transmission originating through the transmitting portion of the distant radio" station may be received through the antenna 131 and by way ofcir- Cult portions .130, 129, 125, 122, 120,14, 13,

become effective withthis line 10, 8, 7 and5 circuit 1; I i

The networks 3 and 4 have electrical characteristics to correspond'with the character istics of the line circuits 1 and 2respectively. Under a connection,'electro-respon In a more detailed description or the present system, a connection corresponding with At the point the one briefly outlined above will now be traced and discussed.- For this, reference will also be'had to Figs. 2, 3.and 4 of thedrawings wherein the transmission conductors proper have, 1n themain, been shown in shaded lines to distinguish from other conductors shown by non-shaded lines.

Under a call from a distantpoint or station 50 on'the l1ne 1 (Fig. 2) a signal 51 will be displayed. In response to this,the plug of cord 7 may be inserted in the jack 5 to disconnect the signal 51, close the main conductors of the line to the coil 10 and at the upper contacts of the jack 5,. complete an obvious circuit from grounded battery to energize a relay tor-connecting the balanc ing network3 with the coil 10. This coil is a balancing unit or the type commonly reterred to in the art as a hybrid coil. A separate coil unit comprising windings 53 serves eases as an autotransformer for presenting a'de-,

sired impedance towards the line section 14.

Operation of a key 54 connects the operators signal '7 will be operated, and at the station C a similar signal (not shown) will also be displayed. In answering this call at B, a plug 62 of the cord circuit 23 may be inserted in jack 21. This disconnect-s the signal 5'7, and with lreys 59 and 60 operated on this cord and keys 61 and 150 operated at A the-telephone set 9 will be connected to the telephone set 39 at B. At the point C equip ment identical with that at B may have been employed in answering this call at thatpoint, in placing a similar telephone set 139 in circuit to A. In tracing this talking circuit from the set 9, the metallic circuit is'over contacts of keys 61, a network 62, bus conductors 63, the alternate sets of contacts of a key 100' to bus conductors 65. Thence, the circuit branches, one path to the line 18 and the other path by way of the normal sets 01 contacts of keys 66 and 67 and line 16 to the jack 21. Tracing the conductor singly from the upper member ofthe plug 62, at the point B, the path is over the upper alternate contacts of key 59 (now operated),-upper normal contacts of a key 68, next upper alternate contacts of the key 60 (now operated), the third left-hand alternate contacts of a key 69 (now operated) receivers 70 of the telephone set 39, the third right-hand alternate contacts or key 69, next lower alternate contacts of key 60, right hand alternate contacts of key 69, right-hand normalcontacts of a key 71, the secondary winding of an induction 1 coil 72, left-hand normal contacts of the key 71, left-hand alternate contacts of key 69, the third upper and the lower alternate contacts of key 60, lower normal contacts of key 68, thence overthe lower alternate contacts of key 59 to'the lower main conductor of the plug 62-. The circuit just traced is typical of the circuits not shown, but present at the point C, therefore, a request from the op erator at A for the desired connection may be simultaneously received by the operators at the points B and C. In this position of the'circuits, the transmission between the three operators will be on the two-wire basis. The operators at B and C now 'proceedto place the equipments incondition for send ing and receiving, respectively. v

For calling over the radio channel, a key 73 may be operated in connecting a calling or signal control device assumed as present at 32, over an obvious circuit to act outwardly over the transmitting antenna; In preparation for the desired connection 31, the cord circuit 22 may be connected to join the jacks 20 and 25, While the corresponding cord 122 may be similarly placed to join the jacks 120 and 125 at the receiving'point.

Under a traific procedure where the attendant at Bmay perform the operation of passing the call over the radio channel, the circuits of the operators set at that point may now be positioned for four-wire working. For this, the transmitter side '72 of the telephone set 39 will be conneetedto the cord circuit 22 while, the receivers 70 will be 0051-,

nected to the cord circuit 23. In this position of the circuits, keys 74. and 75 of the cord 22 will standoperated, keys 59 and60 operated on theicord circuit 23 while keys 69 and 71 of the common equipment willalso stand operated. In tracing the circuit for the operators receivers 70, either signal or speech energy arriving over the receiving antenna 131 tive by Way of the repeater 19-with the main and the connection just described at C, may

conductors of the order-wire circuit ineluding section 16 to the jack 21 in which the plug 62 is nowpresent. Tracing singly from' the upper conductor of this plug,tl1e th includesth'e upper, alternate contacts 0 the key 59, normal contacts of key 68, next upper alternate contacts o'fkey 60, third left-hand alternate contacts of the key 69, receivers 70,

third right-hand alternate contacts of the key 69, next lower alternate contacts of key.

60, right-hand alternate contacts of key 69,

right and left-hand inner sets of contacts of v the key 71, left-hand alternate contacts of key 69, third upper and lower sets'of alternate contacts of key 60, lower normal con tacts of key 68, thence over the lower setof alternate contacts of the key 59 to the lower member of the plug 62. Thus, the receivers 70 now standconnected to the circuits of the receiving antenna 131 at station E. i

The signal transmitter 32 may be arranged so that it may be .set to automatic'ally send out code or call signals for reaching any desired distant radio point or station, the call signals being repeated automatically. Since j the receiving and the sending channels of the radio equipments are independent or on the duplex basis, the key 73 may remain in its operated position sothatcthe call sigmalmay be repeated until thecalled station answers by way of the receiving channel antenna. 131.

In case the answer may be by telegraph or code the operator at B will receive it in the receivers 70, andmay then set the transmitter at 32 fortelegraph sending and communicate with the answering radio station on that basis. In case the response' is by voice, the operator may restore the key 32 and converse with the called station. For this, the renext lower alternate contacts of key 7 5, second right-hand alternate contacts of key 69, right-hand alternate contacts of key 71, secondary winding of induction coil 72, letthand alternate contacts of key 71, second lefthand alternate contacts of key 69, third upper and the lower alternate contacts of key 75,

lower normal contacts of keys 148 and 77,

7 member of the plug 64;. 6

normal contacts of a key 149, thence over the lower alternate contacts of key 7 1 to the lower From the connection at the jack 25 the present transmitting circuit is through the right hand windings o1 a repeating coil 81, the opposite windings of this coil being connected over a loop through the opposite sets of normal contacts of keys 82, 83, 73 and jack 27 to the radio transmitter equipment 30. I

'For convenience of description, the transmission circuit over line 12, the cord circuit 22, and the radio sending system will be referred to as the east channel while the opposite side of the duplex circuit which consists of the radio receiving system as con nected over cord 122 to the transmission section 14: will be indicated as the west channel. V i

The operated position of the key 74 disconnects the end of the cord circuit 22 towards the plug 63 and connects a balancing unit or resistance 158in closing a loop now formed .by the connection which may stand prepared by presence of the plug 63 'in the jack 20 of the line section 12.

From the foregoing it will be clear that the transmitter side of the telephone set 39 may now be effective over that portion of the east channel which includes the right-hand end of the cord circuit as connected to the antenna 31, whilethe receivers of this telephone set will be connected to the west channel as extended over the section 16 of the order line. In this way, the operator at the station B may converse with and request a connection from the distant operator who may have answered the present assumed call. On completion of the connection at the distant point, the operator at B may make any necessary verification by talking directly with the station connected, and assuming that the connection to the station 50 has been retained at A, restoration of the key 74 on the cord 22 will cut the trai'ismittingv circuit through so that the conversation of the connection may proceed. i

It may be pointed out that over the cord circuit 22 the circuit of the through conchannel by means of a so-called monitoring key on the cord circuit 122, similar to a moni toring key 86 of the cord circuit .22, while the operator at A will have had aiccessto the west channel either by means of a monitoringkey (not shown) which may be present on the cord circuit 7, or by means of the key'61 the monitoring at this point may have been car ried out by way ofthe order-wire circuit.

During the period of a connection, the op erator at either or all of the stations A, B and C may monitor in a variety of ways. A first combination will be described whereby the three operators may, while monitoring by way of the order-wire line, speak to each other without afiiecting the circuits or without interfering with the progress of the conversation of the main connection under observation. 7 I

Under one method of monitoring by way of the order-wire line, the plug 62 may continue in the jack 21, the keys 59 and 60 remaining operated, while the keys 69 and 71 may stand in their normal positions at the station B. This places the t'elephone set 39 in the position in which the circuitswere traced, for answering the call from station A over the ord'erline. At the station C, the corresponding cord circuit 123 may be connected with the jack 121 and like keys positioned asat the station B. U The key 61 at station A. may be operated in connecting the telephone set 9 with the order circuit.- Therefore, voice currents originating on the'toll line 1 or voice currents originating at the distant station ofthe connection and manifested over the west channel may become effective through the'receivers of the telephone sets9, 39 and 139 at the respective points A, B and C.

The coupling unit 19 whereby these voice currents from the connection may become efiectlve w1th the order-wire circuit may be formed of'the arrangement shown in Fig. 5.

Conductors from the hybrid coil 10 may connect to an input transformer 87 of a three element vacuum tube amplifier 88, an output transformer 89 of which may connect by way of the normal contacts of a key 90 with busconductors 6 5 of the order-wire circuit. As well understood in the art, this vacuum tube arrangement is conductive in the direction from the: input towards the output side, but substantially opaque in'the opposite direction as fromtheoutput to the input side. There- This is possible due to the unidirectional character of the coupling unit 19 which issubstantially opaque to currents which otherwise would tend to flow from the order-wire circuit into the circuits of the connection, asalready mentioned.

The transfer type key 66 serves for switching the order-wire section 16 from the section 18 to bus-conductors 63. This leaves the monitoring connection with the latter section so that an operator at C may monitor, while the operators at A and-B maybe conversing over the first section 16. The ringing key 67, of cut-oft type, permits the operator at A to apply current from the source 91 in signaling individually to the station B, while at a point 92 it will be understood that keys similar to the keys 66 and 67 may be present for individually signaling and talking from the station A to the station C. Under the last mentioned condition the operator at B may monitor over the section 16 while a conversation may be in progress between the operators at the pointsA and C over the circuit section 18.

In describing an alternate monitoring arrangement, the operator at A may hear both the east andthe west transmissions by way of the unit 19 but independently of the order,- wire circuits. This is accomplished by operation of the key 90 to switch the unit 19 from the bus-conductors to the conductors 63 accessible as already traced, to the telephone set 9. During such monitoring at A the rder-wire circuit will be free for use between the stations A and C. At B the operator may monitor on the east channelb restorinm he s.

69 and '21 and operating the key 86 of the cord circuit 22. For this, a bridge path extends from the upper main conductor over the upper alternate contacts of key 86, left-hand.

winding of a repeating coil 92 and the lower alternate contacts of the key 86 to the opposite or lower main conductor of this cord circuit 22. stand connected respectively over the left and right-hand inner normal contacts of the key. 69 and the upper and lower lnner alternate contacts of the key 86 thence completing circuitthrough the right-hand winding of the coil 92. Respective upper and lower normal contacts of the key 86 disconnect a signaling relay 93 during the monitoring operation.

The impedance of the left-hand winding of the monitoring transformer 92 is high, so that the transmission loss under its connection will be small or inappreciable.

At the station G monitoring on the west r channel may be carried out in a manner aim- The" receivers of the telephone set now ilar to that just describedfor monitoring on the east channel at the station B.

In describing a further monitoring combi- I nation whereby each of the stations A, B and C may hear the transmission in each direction or as commonly expressed in the art, may

hear both sidestof a conversation, let it now be assumed that the key 90 may be in its oper ated position at A in appropriating the regu-v lar monitoring circuit for use 7 at that point only, as already described, while the monitoring key 86 of the cord circuit 22 may be op erated in connecting the receiver through the coil 92 as above described. Now, by inserting theplug 102 of the test cord circuit into the jack 21 of the order-wire line, and, operating key 103 of this cord and key 71 the monitoring energy may divide between the receivers 70 and the order-wire line. At the point C a monitoring key corresponding with the key 86 may stand operated on the cord 122 while the test cord 133 may be connected with jack 121 of the order wire circuit and keys corresponding with keys 103 and 71 may stand operated. In this manner, voice currents from the east and west channels of a connection similar to the one already described, may become effective over the orderwire line with the receivers of the telephone sets 39 and 139 at the points B and C, respectively.

For the last mentioned monitoring arrangement the circuit maybe traced from-the up per member of plug 102, now in jack 21, over the upper normal sets of contacts of keys 104, i

nate contacts of key 86, winding of monitor ing coil 92, next lower alternate contacts of the key 86, inner right-hand normal contacts of key 69,- next lower alternate contacts of key 103, thence over th'elower normal con tacts of keys 108, 106, 107, -and 104 to the lower, main member of the plug 102. Thus, the circuit to the order-wire line forms a second bridge on the right-hand winding. of the monitoring coil 92 the receivers'70 forming the first bridge as already traced. Over the circuit last traced, energy from the east channel will become efiecti ve in the orderwire circuit While the duplicate equipment at station C may similarly supply energy from the West channel; The character of the coil 92 and the correspondin T monitoring coil at point C, while limiting the amount of energy taken from the transmission channels, also provide ineflici'ent coupling in the inverse direction as towards the channel s, res ectivel'y. Therefore, there is little or no tendency for transfer ofenergy between fihe main transto the respective jacks toring on the east channel.

mission channels, by way of this monitoring circuit. The operated position of the key 71 disconnects the circuits of the transmitter side of the telephone set 39 while monitoring as first described.

In situations whereduring so-called busy hour periods a large numberot connections may be handled between the toll center A and a similar distant toll center, the cords 22 and 122'at points B and C may remain connected as described for the as sumed connection in retaining the two radio channels in operative condition with the land lines terminating equipments. Therefore, the operator at A may work directly with the corresponding distant operator relative to disposing oi completed conversations and in carrying out changes in switching at the land line centers in completing new connections. During such periods, the patching'cords 45 or 1&5 may be employed, when desired, ior respectively joining jack 20, and 120, 125 in substitution of the regi r service cords 22 and 122, at the respective points and C. Monitoringmay still be carried out by way of the order-wire line or at the station B one end or the cord 22 may be connected by way of the jack 28 and key 86 operated in moni- 'Ihecord 23 may also be used for this monitoring, at this point B. At the point C either the cord 122 or 123 may be oined to jack 128m similarly monitoring at the latter point. By employing patching cords as just described, the number of devices and contacts in the circuits of a connection is reduced which is an obviously desirable condition.

Ordinarily, when repeaters are required as indicated at lland 13 (Fig. 2) they may be of the so-called one-way type. For example, the repeater 11 may transmit in the direction'iirom A to B, while conversely, the

repeater 13 may transmitin the direction from C to A only. 'lhcr tore, when monitoring at station I3 by way of the key 86, as described, the transmission on one channel only, the cast, will be heard, while under corresponding monitoring at the station C the transmission of the opposite or west channel onlywill be heard. For such reasons, the advantages realized by providing that monitoring may be carried out by way of the order-wire circuit over which the two-way transmissions may be heard will at once be apparent.

The matter of regulating the amount or volume of transmission energy which may reach the radio transmitter is of importance. This is in order to prevent distortion of speeclior to prevent excess of energy beyond certain predetermined limits which would either damage the equipment or result in circuit breaker response on the associated power leads. In either case, interruption and delay would result. To meet this situation, keys 82 and 83 respectively serve for includingor excluding attenuation networks 94 and 95 with the transmission leads. Either one or the other or both of these networks may be in circuit depending on the serv'ce routine at the station. This may vary or differ during'a day or other period at a given station. The unit 94: may be in immediateassociation with the present switching devices, while the unit 95 may be at a point remote thereto as at the radio transmitter proper.

When the key 82 is operated, the key 83 will ordinarily be in its normal position and vice versa. Assuming the key 82 to be operated, the transmission path may be traced from the upper member of the jack 26 second upper alternate contacts of key 82, left-hand resistance of 94: and associated adjustable contact, thence over theupper alternate contacts of the key 82 to the upper main conductor towards the transmitter 30. From the lower member of the jack 26 the other path of the circuit is by way of the next lower alternate contacts of key 82, over a conductor loop to the upper rigl1thand terminal of 94:, thence over the lower alternate contacts of the key 82 to the lower main conductor towards 30. I Vhen the key 83 is operated, paths'in duplicate of those just traced place the unit 95 in circuit to the radio transmitter. By inspection, it will be seen that the units 9e and 95 are of the type commonly referred to in the art as constant impedance gain controls.

In connection with the use of the gain control devices 94: or 95 the meter-system shown in Fig. 6 may be employed. This may correspond with the system of U. S. Patent No. 1.563284%, November 11, 1925, transmission circuits. Insertion of a plug 96 into the jack 28 establishes the right-hand winding of a transformer 97 in bridge on the. main conductors to the radio transmitter 30, while ground potential to the lower conductor of this plug completes an obvious circuit for energizing the filament of a vacuum tube rectifier'98. Each halt-wave of alternating currents by way of the transtormer97, will be rectified and result in a unidirectional energy effect through an indicating device or meter M. A battery cell 99 serves to balance and stabilize the circuits of the rectifier sys tem so that in the absence of incoming alternating currents the needle of the meter may rest at zero, and not be affected by the vacuum tube phenomenon commonly referred to as Edison effect. This meter system is proportioned to present a very high impedance across the transmission circuit, and, there fore, may remain connected during preparation for and the progress of a conversation, thus serving as a guide relative to adjustment of the volumecontrol devices 94 or 95. Other jacks similar to thejack 28 or the additional jack in bridge on the lines 12, 16 and 111 may be present at different desired points on the system and ma y serve for connecting the volmamas POSQS'.

The purpose of a gain control unit of I the cord circuit 22 is principally to allow transmission adjustments at the transmitter 30 and the controls 94 or during periods the operator at B may be speaking over the east radio channel in preparing for a con nection. Operation of the key 149 eiiects obvious switching to insert the network 80 in the circuit already traced from the transmitter of the telephone set 39 to; the main conductors of this cord circuit, the keys .74, 75. 69 and 'i'lvhav'ing been set to their operated positions, When the operator at B maydesire to adjust the controls forefiicient transmission from the toll center A, the gain control 80 may be set to introduce aloss between the operators set 39 and the radio set 30 which wv-ill be equal to the transmissionloss over the circuits between A and the switching point B. There-fore, following adjustments of the radio transmitter and the distant radio receiving devices for this condition of speech from the set 39, substantially no change in speech volume may be experienced when the operator at B, after completing work from that point, may switch the connection through, as already described, for use by the operator at A. In a similar manner the operator at B, may, in speaking over the radio channel, first adjust the control 80 so that a loss'will be introduced equivalent to moving the transmitter of the telephone set 39 back to'the distant station point 50, thus providing that at the proper time in the handling of a connection, no transmission change may result when speech from the point 50 is substituted for speech from the telephone set 39 at point B. o I

At the station A the network 62" is principally to provide for uniformity of distribution of transmissionenergy both for talki-ng over and'for monitoring by way of the order-wire circuit. talk on the order-wire circuit in which the operators at points A, B and 6 may be tak' ing part, the network 62 may be adjusted so that in terms of transmission, the telephone set 9 may be at the same distance from the junction point of the line sections 16 and 18 as the transmission distances from-the stations B and C, respectively, to this junction.

This is also particularly desirable under three-way monitoringwhere the voice currents by way of the hybrid coil 10 are applied at the junction point of the'two sections of the order wire.

It will be understood that a key similar to the key 149 of the network 80" may be provided for inserting or removing the network 62 relative to-the path from thebus-conductors 63 to the telephone set 9 and further, that for monitoring at station A, thecircuits at that point may he arranged: in a manner Under a conference similar to that at the stations B and C, whereby the telephone receiver of the set 9 may be separated from the circuits of the associated transmitter, and alone applied to the circuits for monitoring purposes.

In describing the handling of a wire radio connection at the point B inde pendently of the switching center A, let it now be assumed that a call from a point on a line 1 11, effects display of a signal 112. In answering this. call either one of the cords 22, 23 or 33 may be used. Assuming that the cord 33 is used, plug 102 may be inserted inthe j ack24 thereby disconnecting the signal 112,-and extending the line 111 so that operation of key 103 will place the telephone set 3.9 in circuit to receivethe request from point 110. Plug 113 may now be insorted into jack21 of the order circuit, a splitting key 114 operated, then the ringing key 68 momentarily operated in applying current from a source to operate asignal (not shown) on the order circuit at station C where the call may be answered and request received from the operator at B that the west channel be connected to the order circuit.

The latter may be effected by joining jacks and by means of the cord circuit 122.

At the station B, a patching cord similar to 45 may be substituted for cord 33 at the jack-24a and its opposite end connected to the jack 43. The plug 62 of the cord 23' may be i'nsertedinto jack 44 while plugs 63 and 64 of cord circuit 22 may be respectively insert-ed into jacks 42 and 25. This places the two-wiroline' circuit 111 in circuit to the hybrid coil .40, whence a branching four-wire circuit is. derived in which the east radio channel will be connected by cord 22' to jack.

4 2 while the/westchannel will be connected by way of the order circuit, cord 23 and the jack 44. A call signal may now be sent from the point B over the radio transmitting system 30 in' the same manner as that already described, while re 1y may be receivcdover the west channeLJ pll itting keys Hand 114, talking keys 75 and 6010f the cords 22' and 23, and keys 69 and 71 may now stand operated,

the transmitter circuit 72 of the telephone set 39 will then be connected over'the east channel, while the receivers 70 will be con nected over the west channel for talking over r the radio equipments. When the radio side of'the desi red connection is in readiness, the splitting keys 74 and 114 may be restored in completing the connection through to the line 1 11, so that the conversation may proceed. Restoration of the splitting keys 74 and 114 also disconnects the telephone set 39. V

The keys 75 and 60 may continue operated without eflect until keys 11 6 and 86 may be operated, thereby permitting the telephone set 39 to be applied in bridge on the 4-wire side of'the connection. The keys 69 and 71 remain operated so that the'transmitter circuits of the telephone set will be connected to the east channel while the receiver of the set will be connected to the west channel.

Speech originating at the set 39 may then.

- phone set 39.

In. tracing the transmitter circuit, the path is from the upper main conductor of the'cord 22, upper contacts of the key 116, next upper alternate contacts of key 75, inner left and right hand alternate contacts of key 69, next lower alternate contacts of key 75, second right-hand alternate contacts of key 69, righthand alternate contacts of key 71, secondary winding of the induction coil 72. leit-hand alternate contacts of key 71, second left-hand alternate contacts of key 69, third upper and the loweralternate contacts or key '75, thence over the lower contacts of key 116 to the lower main conductor of the cord circuit 22. The circuit for the receivers is from the upper main conductor of the cord 23 over the upper contacts of key 68 next upper alternate contacts of key 60, third left-hand alternate contacts of key 69, receivers 70, third right-hand alternate contacts of key 69, next lower alternate contacts 01"" key 60, right-hand alternate contacts of key 69, right and left-hand inner alternate contacts of key 71, left-hand alternate contacts of key 69, third upper and the lower alternate contact of key 60, thence over the lower contacts of key 68 to the lower main conductor of the cord circuit 23.

The operator at station B may monitor on this connection over either the cord 22 or 23. Assuming new that the keys 75, 116 and 60,

68 are restored and a monitoring key 117 on cord circuit 23 is operated, the upper and lower alternate contacts of this key establish the primary winding of a high impedance monitoring coil 118 in bridge on the two main conductors of the cord circuit. Assuming that the keys 69 and 71 are still in their operated positions, a loop may be traced from the upper end or the secondary winding of the coil 118 over the next upper alternate contact of key 117, third lef -hand alternate contacts of key 69, receivers 70, third righthand alternate contacts of key 69, and the next lower alternate contacts of key 117 to the lower end of the secondary winding on this monitoring coil 118. i

In monitoring overthe circuit just traced, voice currents originating at the station 110 as well as currents originating at distant point served by the radio channels, may bev come effective with the receivers of the telephone set 39. This is due to the fact that currents from the line 111 may branch through the hybrid coil 10 into the receiving'as well as into the sending side of the four-wire or duplex circuit, whilethe cord circuit 23 forms a link in the channel over which voice currents are conveyed from the distant station duced at points intermediate the hybrid coil a0 and respectivejacks 42 and 44, in the same relation in which the repeaters 11 and 13 are connected in the four-wire circuits from the hybrid coil 10, then only one side of a c0nversation may beheard in the receivers 70 when monitorin by way of the cord circuit 23. The reason for this is rendered clear by the description already given in connection with monitoring operations under the first assumed connection.

When desired, in handling connections similar to the one last described, the cordeircuit 23 and the patching cord 45 may be interchanged, so that the latter cord may join the jacks 21 and 44; while the cord 23 will join jacks 24 and 43. This places the cord circuit 23 as a link to join the line 111 to the hybrid coil 10. Therefore, the operators set '39. and other associated controls may be applied on a two-wire section of the present connection. For this, the key 69 may be operated while the key 71 may stand in its normal position so that talking or monitoring may be carried out from the telephone set as will be readily understood from the descriptions already given for the first assumed connection. In monitoring, both sides of the conversation will be effective in the receivers 7 O.

In case a call signal may originate at point 110 during the period of the last assumed connection, arelay 119, of high impedance and normally connected by way oi upper and lower normal contact of key 117 in bridge on the main conductors of the cord circuit will respond. This closes an obvious circuit from battery through a signal 151, which responds and closes an obvious circuit'from. the same battery through an audible signal 152.

lVhen it may be desired to signal the station 110 from the cord circuit, and assuming llll that the plug 62 is present in the jack2 r,

splitting key 159 may be operated followed by momentary operation of key 68. 7 Energy from the source 115 may traverse the alternate contacts of keys 168 and 59' thence overthe upper members of .plug'62 and Jack 24, a loop formed by the line 111', thence over the lower main members of this jack and plug and the lower alternate contacts of the keys 59 and 68 to the source 115. Incase the plug 113 had been present in the ack 24 the splitting key 114 rather than the key 59 would have been operated. Following this the same signaling key "'68 would have been operated and energy fromsource 115 wouldthen traverse the upper alternate contacts of key "68 upper normal contacts of key 59, upper alternate contacts of key 114, thence over the upper member of the plug 113 to return .over the lower main member of this plug, lower alternate'contacts of key 114, normal contacts of a key 154 of a gain control unit 153,1the lower normal contacts of the 'key59, and the lower alternate contacts of the key 68 to this source 115.

In situations where provision is made for signaling over the radio channels as shown in Patent No. 1,624,672, granted to H. W. ONeill, April 27, 1927, calling may be citeded by keys 68 or 148 of the cord circuits 23 and 22 in a manner similar to that just described jfor signaling over the line 111. The signaling cur-rent to be applied, of course, is over that portion of a cord circuit which may be joined to one of the jacks 28 of the radio transmitting channel.

At the station 0 .a line similar to the line 111 may be assumed as terminating in the jack 134, and the operator at C may establish a connection from-such line to the radio chan} nels. For this, cord 123 may join jacks 124 and 143, patching cord 145 may Join jack 142 with jack 121 ot'the'orde'r circuit, while cord,

122 may join jacks 144 and 125. Over the order wire circuit a request maybe made for the operator at B to connect jack. 21 of the order wire circuit with jack 25 of the radio I channel. From the description already given of the handling of the assumed oonnectioni'rom the line 111 at B, it will be obvious how the duplicate switching apparatus at C may be handled in providing a wire-radio connection for the line circuit of the jack 124.

In situations where it may be desired, signaling keys similar to the key 67 maybe inserted at points 155 and 1'56on the line sections '12 and 14 respectively,for control of a call si nal 157 at the jack 20 and a similar signal (not shown) which may be present at the jack 120. By such means, the operatorat A may signal or call the operator at B or at C independently of the order wire circuit, while during periods either the cord circuit22 or 23 may be connected to the jack 20, operation of V a key at point 155 may effect response of relay 93 and in turn operation of audible signal 152; In like manner, a key at point 156may control either a line signal ora cord signal at the station C. From the drawing, it will be clear that the contacts of the line signals 57, 112 and 157 ma close an obvious circuit to energize the audible si nal 152. v

It may be pointed out t at at radio trans mitt-ing stations, the high frequency currents set up extraneous fields which maybe manifested over areas occupied by radio transmitting equipments and also equipments and circuits in whichassociated land lines may terminate. Notwithstanding, the use of protecting measures as shielding and "balanced connections to earth, such currents may, at times, reach the circuits and equipments not intended for currents at radio frequencies. In paths Wheredirectcurrents may'norinally be present,jhigh fre uency currents may act or discharge throu'g the insu-.

lati'on or conductors, coils and the like, following which, the direct current'ma flow and establish a permanent fau t- In addition to interruption of service, such faults introduce a certain amount of personal injury hazard'as following aso-called .cutting through of the high frequencycurrents, direct currents or currents of'lower frequency but perhaps of high potentials,

commonly required with radio transmitting systems, may energize circuit parts with which operators or attendants come into con tact. In order to afiord a certain amount of thenv protection to the operators and equipments,

the present circuits have been planned particularly to a'iford substantially zero resist- To the end that certain extent, protected due to thepronimity of the associated grounded strand. This provides that in the event that high frequency currents or discharge efi'ects may reach the voice transmission circuits'in sulficient volume to constitute a hazard, they will generally pass to ground over the sleeve strand of a cord iandordina-rily may not cause a tron:

of dissipation. 7 I

In order that'determinations may be quickly made as to unbalance of the transmission ble condition to continue to exist at-the point circuits, discovering the nature ofirregulani-v ties, and for locating the point at which an irregularity may be present, the-cordcircuit 33 has been arranged as azcombinedsarvice and .testing cord, A jack 34 provides fon'connection of either a suitable type 0f Whe'at'stone bridge, an impedance bridge,

which may be of the type shown in U. S. Patent No. 1,4;Oa,311, January 2 1, 1922, or a combined voltammeter system 131 shown in the drawin Insertion of a plug 161 into the jack 34 connects the meter system which comprises a meter V, a scale changing key 162, a meter shunt control key 163, a test battery 160and a circuit reversing key 164. f In making tests, the plug 102 may be inserted into any of the jacks oi? the various equipments shown. The circuits have been arranged so that either so-called out-going tests or incoming tests may be carried out. It'is believed that by tracing the test circuits only to the main members of the plug 102 that a clear understanding of the system may be had. Outgoing tests is the term commonly applied to tests made from a point at which the current indicating devices may be present, while incoming tests refer to switching effects carried out for the conven- 34.- (now vacant) ience 01' an attendant who may be making outgoing tests at a distant point on the same circuits.

For incoming tests, operation of key 10 1 connects ground by way of the upper normal contacts of key 107, normal contacts or jack and the upper alternate contacts of the key 10 1 to the upper member of the plug. The circuit from the lower main member or this plug now stands open at the lower normal contacts of the key 10 1.. Operation of key 105 establishes an inverse effeet by grounding the lower main member while opening the circuit to the upper member of this plug 102. Gperation of key 107 joins the upper to the lower main member of the plug 102. This may be traced from the upper member over the upper normal contacts or keys 10-1, 105 and 106, the upper alternate contacts of key 107, contacts of jack 3%, lower alternate contacts of key 107, thence overthe lower normal'contacts of keys 104: and 105 to the lower main member of the plug 102. Operation of key 106 insures opening of the circuits from the plug 102 irrespective of whether the telephone set 39 may be connected due to an operated position of the talking key 103, as already described. Current from the source 115 may be applied to the main members of the plug 102 by operation of key 108.

For outward tests, plug 161 may be inserted into the jack 3-1. his operates the normally closed contacts of this jack and prepares a circuit from ground o er the upper normal contacts of key 107, the lower main members of jack 3 1 and plug 161, upper nor mal contacts of key 164;, normal contacts of key 162, the meter V, battery 160, the lower normal contacts of key 164-, the upper members of the plug and jack, thence to stand. open at the lower alternate contacts of keys 107 and 105 and the upper alternate contacts of key 104. Therefore, operation of the key 104 will place the series formed by the battery 160 and meter V in series from ground to the upper member of the plug102, while the circuit to the other main member of this plug will stand open. 1 Operation of key 105 con nects the battery and meter in a like manner to the lower main member of the plug 102,

while the circuit to the upper member willbe opened. Operation of the key 107 disconnects the ground and places the series formed by the meter V and battery 160 in a loop to the main members or the plu 102. Opera tion of the key 16 1 reverses the polarity re-/ lation of the meter V relative to the battery 160, Tests to determine the continuity or insulation ot conductors are usually made with the keys162 and 163 positioned as shown. Approximate determinations as to the resistance ot a circuit may more readily be made 7 by operating the shunt control key 163, while current readings may be made by operating key 162 to connect-the active'winding only of the meter V. i

In connecting a W'heatst-one bridge or the impedance bridge of Patent No. 1, 104,311 above mentioned, the X terminals or terminals ot' the unknown, may be provided with either with the cord circuit 22 or the cord cir- Y cuit 23 on a 2-wire control basis. This being carried out in a manner to entirely disconnect the leads to the cord circuit vacated, so that in the event of irregularity in the operation of one of the cord circuits, the other cord cir cuit may be substituted.

The key 71 serves for either joining or separating the circuits of the receivers from the circuits of the transmitter of the telephone set 39. Under aseparated condition of the receiver and transmitter circuits, the system will be on a li-wire basis relatiye to control'by way of the two 2-wire cord circuits 22 and 23. In thisv position of the circuits, the key 69 serves as a transposing key whereby the receiver and the transmitter circuits may be interchanged, respectively, relative to connection with the two cordsv For example, when the key 69 is normal (key 71 operated) the receivers ot the set 39 will be connected to the cord 22'while the transmitter will be connected to the cord 23, and inversely, when the key 69 is operated, the receivers will be connected to the cord 23 while the transmitter will be connected to the cord 22.

During periods the key 71 may be in its operated position, the circuits of the receivers 70 will also stand prepared to the key 103 for use with the combined service and test cord 33. Therefore when the key 69 is in its normal position the cord 33'may serve as the receiving side, while the cord circuit 23 may portion or side of a l-wire circuit. a

In establishing connections with the radio transmit-ting system at B, the 121Cli-25 1S'111- ployed in situations Where it may be desired to guard against the possibility of ircct currents reaching the radio system, or, inversely,

in insuringthat direct currents from the radio equipment may not enter the terminating circuits of lines which may be connected. transformer 81 serves as an insulating or blocking means against such dir ct currents, This transformer or repeating coil may also be of an unequal ratiotype in providing that proper impedance relations may he had in coupling certain circuits to the radio equip.

ment.

Connections may be made by way of the jack 26 in situations Where it may not be necessary to observe the points mentioned next above. Insertion of a plug into this jack 26 disconnects thetransiormer 81 and also the jaclr25. Connection may also bemade at the jack 27 where insertion of a plug will dis-= connect all of the equipment to the left of this jack and afiord a connection directly to the main conductors leading into the radio transmitter 30.

What is claimed is: v 1. In a radio-wire telephone system, a transmission circuit formed of a first land line and a radio section, means vfor applycommunication energy in either direction over said transmissioncircuit, a second circuit, means for applying communication energy in either direction over said second circuit, and means for conducting communication energy from said transmission circuit to said second 0' cuit while excluding coinmunica-tion energy of said second-circuit from said transmission circuit.

2. In a radio-wire telephone system, a transmission circuit formed of a land line section and a radio section, means for communicating over said circuit, a monitoring line and a plurality of telephone sets therefor, a derived path to join said transmission circuit to said monitoring line, and means to render said derived path conductive only in the direction from said transmission circuit to said monitoring line. r

3. In a radiowire telephone system, land lines, radio channels, a plurality of switching points for establishing a connection by way of said land lines and said radio channels,

The

an independent circuit for, communication between said switching points, couplingvv from a certain one ofsaid 2-wire lines, and

branching the 4-wire circuit to said second and third points, a radio transmitting channel and a radio receiving channel-served by 7 said second and third points, respectively, an independenttwo wire circuit joining said second and third points, 2-wire link circuits at said first point for establishing a connection between said. certain circ'uitcand other of the 2-wire circuits at that point, 4-wire link circuits at the secondand third points for completing the connection from the branching paths of said 4-wire circuit to the radio transmitting and receivingchannels, respectively, and also effectingconnection with said independent circuit so that duplex,

operation may becarried out from the sec- 0nd and third points over either the land linesportion or the radio portion of the connection;

5. In a radio-wire telephone system, a plurality of land lines,.a plurality of radio chain nels, testing means including a test cord circuit for localizing faults on said lines-andsaid channels, a service cord circuit for use with said lines and channels, a telephone set connected'ona two-wire basis toeach of said cords, means to render said cords effective on a four-wire basis with said lines, and With said channels, and switching means for changing the connection of said telephone set from the two-wire toa four-wire basis on said cord circuit.

6. In a radio-wiretelcphone system, a :plurality of land lines, a. plurality of radio channels, a plurality of switching'points, circuit control means at said pointsfcooperatively' to servecone point with the others inestab-. lishing a connection from said landlines to effect duplex transmission :by way of said' radio channels, first monitoring means individual to each of thepoints for respectively supervising the transmission of sa d connect on, and second monitoring means common I to all of said transmission; I

7. In a radio wire telephone system, a

points for also supervising said plurality of land lines, a plurality of radio:

for said cord circuits, monitoring means for association with said cord circuits, and switching means to disable said signaling means while enabling said monitoring means. 8. In a radio-wire telephone system, land lines, radio channels, a first and a second cord circuit for connecting said lines to said channels, a telephone set having normally separated transmitter and receiver circuits, a key on each cord circuit for joining said transmitter and receiver circuits in connecting said telephone set respectively to said cord circuits, a key forcagain separating said transmitter and receiver circuits, and a key to transpose the relation of said transmitter and receiver circuits so that either circuit may be applied .by way off the first mentioned keys to either the first or the second cord circuit, respectively.

9.. In a radio-wire telephone system, land.

lines and radio channels, a telephone set including a transmitting circuit and a receiving circuit, a first and a second cord circuit for connecting said telephone set to said lines and channels, a key on each cord circuit for joining said transmitting and said receiving circuits in connecting said telephone set to said cord circuit-s respectively, a first master key to selectively limit the connection of said telephone set to one or the other of said cord circuits and a second master key to separate said transmitter and receiver circuits/in rendering said first master key effective to switch the transmitter circuit to one cord circuit and the receiver circuit to the other cord circuit and ViCB versa.

10. In a radio-wire telephone system, line circuits and radio channels, a first and a second service cord circuit and a test cord circuit for use with said lines and channcls,a telephone set including a transmitting and a receiving circuit, a key oneac-h service cord circuit to respectively connect the telephone set to the cord circuits and normally to eii'ect separation of the transmitter and receiver cir cuits at these cords, a master key intercon- -ected with the keys of the service cords to render the telephone selectively effective with but one or these cords at one time, a key for connecting the telephone to the test cord and interconnections between said telephone set, master key and the keys of tie service cords to effect normal joinder oi said transmitting and receiving circuit at the key or said test cord circuit.

11. In a, radio-wire telephone system, a telephone including a transmitter and a receiver circuit, a first key for joining or separating said transmitter and receiver circuits, a plurality of cord circuits, land lines and radio channels connectively accessible to .L San said cord circuits, switching means for each troducing predetermined amounts of tran mission loss for eachcord circuit, and a splitting key for each cord circuit for elec tiically dividing the cord into two sections while inserting the associated network between said telephone set and one section of the cord circuit. 7

13. In a radio-wire telephone system, a telephone set including a transmitter and a receiver, separate circuits for said transmitter receiver, land lines and radio channels, service cord circuits for use with said lines and channels, testing means includinga cord circuit for use with said lines and channels, a talking key for each of said service cords at which the circuits of the transmitter and receiver will normally stand separated, a talking key for said testing cord circuit at which the transmitter and receiver circuits will stand normally joined, and a monitoring key on each of said service cords to connect said receiver circuit only to the associated cord circuit. I I

is. In a sound transmisison system, a transmission circuit comprising a chain of transmission channels, means 'forapplying sound transmission energy in either direction over said transmission circuit, a second circuit, means for applying sound transmission energy in either direction over said second circuit and means for conducting sound transmission energy from saidti'ansmisison circuit to said second circuit while excluding sound transmission energy of said second circuit from said transmission circuit.

15. In a communication system, communication channels, a plurality of switching points for establishing a connection between said channels, an independent circuit for communication between said switching points, coupling means to establish a derived path from said connection to said independent circuit and means to render said derived path ineffective to conduct from said independent circuit into the circuit of said connection.

In vitness whereof, I hereunto subscribe my name this 18th day of October A. 1)., 1926;

HENRY W. ONEILL. 

